There are 2+3+5+3 = 13 leaves total. This represents tickets were sold on 13 days.
Each stem and leaf combines to form a different ticket count. For instance, the stem of 1 and leaf of 8 combine to get the value 18. So 18 tickets were sold on that particular day.
Inverse operations are operations that undo each other. In this case, 10 + 2 = 12, and 12 - 2 = 10 A multiplication example could be 4 x 2 = 8, and 8 ÷ 2 = 4